This is correct for NN < 4 and IE < 3. NN 4 and IE 3 have limited and partially buggy CSS support. But since they aren't used anymore that much, this is hardly a problem. You you absolutely need to support old browsers, you can either use tag attributes only or use both CSS and attributes. However, many formatting attributes are deprecated in HTML4/XHTML and use of CSS for formatting is strongly encouraged by W3C.

If I absolutely had to support IE3-- and NS4-- (after I shot myself in the foot) I'd sniff out those browsers and send them to a compatible page, with only font tags... much easier than trying to figure out the compatibility inconsistancies between the browsers...